When used correctly, the upper body can greatly contribute to an athlete's sprint speed. The key to unlocking upper body power is learning to keep the arms in a 90 degree bend and driving the elbow backwards as forcefully as possible. Tech Bands immediately alert athletes to any deviations from an ideal 90 degree bend. If an athlete opens their arm to an angle greater than 90 degrees (a common mistake) then the Tech Band will pop off. This is an especially good teaching tool for young athletes.Tech Bands come in bags of 20.